The present invention relates in general to gear assemblies and in particular to a spacer for facilitating assembly of such gear assemblies, including the method of using the spacer.
Gear drive systems relevant to the present invention typically are used in motorized vehicles, such as automobiles or golf carts, which have left-side and right-side driving wheels. In such applications, the gear drive system is positioned within a housing and receives power from a motor or other power source via an input shaft. The input shaft transfers that power via output shaft(s) to each of the left- and right-side driving wheels. One example of such gear drive systems is a differential gear assembly used in a transaxle of, for instance, a golf cart. The differential gear assembly divides power between the left- and right-side driving wheels and permits these two wheels to rotate at different speeds when the vehicle turns.
Differential gear assemblies generally are complex structures having many interrelated parts that must be assembled within one or more housings. Thus, assembling and disassembling these structures can be time consuming and, when assembled in mass-production fashion, even incremental increases in time-efficiency can provide significant benefit. One of the difficulties encountered in assembling single-piece housing differential gear assemblies is fixing the opposing output shafts axially with respect to one another. Typically, a significant amount of movement along the longitudinal axis of at least one of the output shafts is required to permit installation and proper positioning of the gears (and in some instances, rotating internal housings) relative to the outer housing of the differential gear assembly. This axial movement must be eliminated by fixing the output shafts in the longitudinal direction relative to one another. In prior art differential gear assemblies, such fixing has been accomplished by installing a multi-piece spacer, usually a two-piece collar, around at least one of the output shafts, thereby occupying any space that would permit axial movement of the output shaft. The difficulty with such multi-piece locking assemblies is that they are cumbersome to install and remove, slowing the assembly and disassembly processes and increasing per-unit cost for differential gear assemblies. Similarly, disassembly and reassembly for repair is cumbersome increasing the cost of repairing such differential gear assemblies.
Other types of gear drive systems of relevance include non-differential gear assemblies situated within a housing. An example of one such non-differential gear assembly is a transaxle having a xe2x80x9cstraightxe2x80x9d or single axle that extends between a pair of opposed driving wheels wherein a drive gear is non-rotatably fixed to the single axle by a retainer, usually a key/keyway feature. Again, assembly may require that the drive gear or axle or the entire assembly including the drive gear and axle be slidable in one direction or the other (longitudinally with respect to the axle) to facilitate installation of, for example, a key within the keyway. As discussed above, longitudinal movement of this nature must be at least substantially eliminated in the assembled gear drive system to provide proper alignment and functioning. A spacer is used to eliminate such movement. As discussed above, prior art spacers have consisted of those that are multi-piece, surround the shaft, and require a fastener such as a bolt to be installed to retain the pieces of the spacer on the shaft. The prior art spacers as applied to these types of gear drive systems present the same difficulties discussed above concerning differential gear drive systems.
The present invention overcomes the difficulties presented by prior art multi-piece spacers by providing a single-piece spacer that is simply slipped into place and which is retained without the need to install fasteners into the spacer.
It should be understood that the present invention is intended to have application in all such differential and non-differential gear drive systems that are positioned within housings wherein a spacer is required to limit movement in a longitudinal direction of the housing and output shaft(s) after assembly of the gear drive system.
Briefly stated, the present invention includes a differential including a housing having a cavity, a service port in communication with the cavity, and a pair of opposed, axially aligned apertures in communication with the cavity. Each of the apertures is aligned along a longitudinal axis of the housing. A first output shaft is positioned in one of the apertures and is at least substantially aligned with the longitudinal axis. The first output shaft includes a first inboard end within the cavity. A second output shaft is positioned in the other of the apertures and is at least substantially aligned with the longitudinal axis. The second output shaft has a second inboard end within the cavity. A first gear is positioned on the inboard end of the first output shaft. A second gear is positioned on the inboard end of the second output shaft. At least one of the first and second gears has a predefined range of travel in the direction of the longitudinal axis of the housing. A gear assembly within the cavity is in operative engagement with the first and second gears and transfers power to the first and second output shafts via the first and second gears. A spacer is positioned proximate the service port between the housing and one of the first and second gears. The spacer is configured to preclude movement of the at least one of the first and second gears through at least substantially all the predefined range of travel. A cover covers at least a portion of the service port. The cover has an inner surface, the inner surface being proximate the spacer and retaining the spacer in position between the housing and the one of the first and second gears.
In another aspect, the invention includes a method of assembling a differential including positioning a first output shaft in a first aperture in a housing, the first aperture being in communication with a cavity within the housing. A first gear is positioned on an inboard end of the first output shaft, the first gear being within the cavity. A gear assembly is positioned in the cavity of the housing, the gear assembly being operatively engaged with the first gear. A second output shaft is positioned in a second aperture in the housing, the second aperture is at least substantially aligned with, and opposed to, the first aperture. The second aperture is in communication with the cavity. A second gear is positioned on an inboard end of a second output shaft, within the cavity. The gear assembly is operatively engaged with the second gear. A spacer is positioned within the cavity and the spacer is positioned between one of the first and second gears and the housing. A cover is positioned over at least a portion of a service port of the housing. The service port is in communication with the cavity. The cover includes a land which is proximate the spacer and retains the spacer in position between the housing and the one of the first and second gears.
In yet another aspect, the invention includes a gear drive assembly having a housing with a cavity therein, a service port in communication with the cavity, and a pair of opposed, axially aligned apertures in communication with the cavity. Each of the apertures is aligned along a longitudinal axis of the housing. An output shaft is positioned within the apertures and is at least substantially aligned with the longitudinal axis. A drive gear is fixedly positioned on the output shaft. The drive gear is within the cavity. The output shaft has a predefined range of accessible travel in the direction of the longitudinal axis. A retainer fixedly secures the drive gear to the output shaft. A spacer is positioned proximate the service port and between the housing and the drive gear. The spacer is configured to preclude movement of the output shaft through at least substantially all the predefined range of accessible travel. A cover covers at least a portion of the service port. The cover includes a land proximate the spacer and which retains the spacer in position between the housing and the drive gear.